Add support for context diffs

Author: kit-ty-kate

src/patch.ml

@@ -15,6 +15,10 @@ type parse_error = {
   (* TODO: add the start position of the error *)
 }
 
+type diff_kind =
+  | Unified_diff
+  | Context_diff
+
 exception Parse_error of parse_error
 
 let unified_diff ~mine_no_nl ~their_no_nl hunk =
@@ -129,21 +133,25 @@ let to_start_len data =
      (* TODO: investigate start line. This shouldn't be start - 1 but the output of diff is also inconsistent *)
      (st, len)
 
-let count_to_sl_sl data =
-  if String.is_prefix ~prefix:"@@ -" data then
-    (* input: "@@ -19,23 +19,12 @@ bla" *)
-    (* output: ((19,23), (19, 12)) *)
-    match List.filter (function "" -> false | _ -> true) (String.cuts '@' data) with
-    | numbers::_ ->
-       let nums = String.trim numbers in
-       (match String.cut ' ' nums with
-        | None -> invalid_arg "couldn't find space in count"
-        | Some (mine, theirs) -> Some (to_start_len mine, to_start_len theirs))
-    | _ -> invalid_arg "broken line!"
-  else
-    None
+let count_to_sl_sl diff_kind data =
+  match diff_kind with
+  | Unified_diff ->
+      if String.is_prefix ~prefix:"@@ -" data then
+        (* input: "@@ -19,23 +19,12 @@ bla" *)
+        (* output: ((19,23), (19, 12)) *)
+        match List.filter (function "" -> false | _ -> true) (String.cuts '@' data) with
+        | numbers::_ ->
+            let nums = String.trim numbers in
+            (match String.cut ' ' nums with
+             | None -> invalid_arg "couldn't find space in count"
+             | Some (mine, theirs) -> Some (to_start_len mine, to_start_len theirs))
+        | _ -> invalid_arg "broken line!"
+      else
+        None
+  | Context_diff ->
+      assert false
 
-let sort_into_bags ~counter:(mine_len, their_len) dir mine their m_nl t_nl str =
+let sort_into_bags diff_kind ~counter:(mine_len, their_len) dir mine their m_nl t_nl str =
   let both data =
     if m_nl || t_nl then
       failwith "\"no newline at the end of file\" is not at the end of the file";
@@ -157,26 +165,36 @@ let sort_into_bags ~counter:(mine_len, their_len) dir mine their m_nl t_nl str =
     None
   else if str_len = 0 then
     both "" (* NOTE: this should technically be a parse error but GNU patch accepts that and some patches in opam-repository do use this behaviour *)
-  else match String.get str 0, String.slice ~start:1 str with
-    | ' ', data ->
+  else
+    let data =
+      let start = match diff_kind with
+        | Unified_diff -> 1
+        | Context_diff when str_len = 1 -> failwith "bad context diff"
+        | Context_diff when str.[1] = ' ' || str.[1] = '\t' -> 2
+        | Context_diff -> 1
+      in
+      String.slice ~start str
+    in
+    match String.get str 0, diff_kind with
+    | ' ', _ ->
         both data
-    | '\t', data ->
+    | '\t', _ ->
         both ("\t"^data) (* NOTE: not valid but accepted by GNU patch *)
-    | '+', data ->
+    | '+', _ ->
         if t_nl then
           failwith "\"no newline at the end of file\" is not at the end of the file";
         if their_len = 0 then
           failwith "invalid patch (+ size exhausted)";
         let counter = (mine_len, their_len - 1) in
         Some (counter, `Their, mine, (data :: their), m_nl, t_nl)
-    | '-', data ->
+    | '-', _ | '!', Context_diff ->
         if m_nl then
           failwith "\"no newline at the end of file\" is not at the end of the file";
         if mine_len = 0 then
           failwith "invalid patch (- size exhausted)";
         let counter = (mine_len - 1, their_len) in
         Some (counter, `Mine, (data :: mine), their, m_nl, t_nl)
-    | '\\', _data ->
+    | '\\', _ ->
       (* NOTE: Any line starting with '\' is taken as if it was
          '\ No newline at end of file' by GNU patch so we do the same *)
       (* diff: 'No newline at end of file' turns out to be context-sensitive *)
@@ -189,10 +207,10 @@ let sort_into_bags ~counter:(mine_len, their_len) dir mine their m_nl t_nl str =
       in
       let counter = (mine_len, their_len) in
       Some (counter, dir, mine, their, my_nl, their_nl)
-    | _ -> failwith "invalid patch (unknown character)"
+    | _, _ -> failwith "invalid patch (unknown character)"
 
-let to_hunk count data mine_no_nl their_no_nl =
-  match count_to_sl_sl count with
+let to_hunk diff_kind count data mine_no_nl their_no_nl =
+  match count_to_sl_sl diff_kind count with
   | None -> None, mine_no_nl, their_no_nl, count :: data
   | Some ((mine_start, mine_len), (their_start, their_len)) ->
     let counter = (mine_len, their_len) in
@@ -202,18 +220,22 @@ let to_hunk count data mine_no_nl their_no_nl =
       | [""] when counter = (2, 2) -> (List.rev ("" :: "" :: mine), List.rev ("" :: "" :: their), mine_no_nl, their_no_nl, []) (* GNU patch behaviour *)
       | [""] when counter = (3, 3) -> (List.rev ("" :: "" :: "" :: mine), List.rev ("" :: "" :: "" :: their), mine_no_nl, their_no_nl, []) (* GNU patch behaviour *)
       | [] | [""] -> failwith "bad file"
-      | x::xs -> match sort_into_bags ~counter dir mine their mine_no_nl their_no_nl x with
+      | x::xs -> match sort_into_bags diff_kind ~counter dir mine their mine_no_nl their_no_nl x with
         | Some (counter, dir, mine, their, mine_no_nl', their_no_nl') -> step ~counter dir mine their mine_no_nl' their_no_nl' xs
         | None -> (List.rev mine, List.rev their, mine_no_nl, their_no_nl, x :: xs)
     in
     let mine, their, mine_no_nl, their_no_nl, rest = step ~counter `Both [] [] mine_no_nl their_no_nl data in
     (Some { mine_start ; mine_len ; mine ; their_start ; their_len ; their }, mine_no_nl, their_no_nl, rest)
 
-let rec to_hunks (mine_no_nl, their_no_nl, acc) = function
-  | [] -> (List.rev acc, mine_no_nl, their_no_nl, [])
-  | count::data -> match to_hunk count data mine_no_nl their_no_nl with
-    | None, mine_no_nl, their_no_nl, rest -> List.rev acc, mine_no_nl, their_no_nl, rest
-    | Some hunk, mine_no_nl, their_no_nl, rest -> to_hunks (mine_no_nl, their_no_nl, hunk :: acc) rest
+let rec to_hunks diff_kind (mine_no_nl, their_no_nl, acc) l = match diff_kind, l with
+  | _, [] -> (List.rev acc, mine_no_nl, their_no_nl, [])
+  | Unified_diff, count::data | Context_diff, "********"::count::data ->
+      begin match to_hunk diff_kind count data mine_no_nl their_no_nl with
+      | None, mine_no_nl, their_no_nl, rest -> List.rev acc, mine_no_nl, their_no_nl, rest
+      | Some hunk, mine_no_nl, their_no_nl, rest -> to_hunks diff_kind (mine_no_nl, their_no_nl, hunk :: acc) rest
+      end
+  | Context_diff, _::xs ->
+      to_hunks diff_kind (mine_no_nl, their_no_nl, acc) xs
 
 type operation =
   | Edit of string * string
@@ -348,13 +370,13 @@ let parse_one ~p data =
   in
   (* first locate --- and +++ lines *)
   let rec find_start ~mode ~git_action = function
-    | [] -> git_action, []
+    | [] -> git_action, Unified_diff, []
     | x::xs when String.is_prefix ~prefix:"diff --git " x ->
         let git_filename = Fname.parse_git_header (String.slice ~start:11 x) in
         begin match mode, git_action with
         | (None | Some (Git _)), None -> find_start ~mode:(Some (Git git_filename)) ~git_action:None xs
         | None, Some _ -> assert false (* impossible state *)
-        | Some (Git _), Some git_action -> (Some git_action, x :: xs)
+        | Some (Git _), Some git_action -> (Some git_action, Unified_diff, x :: xs)
         end
     | x::y::xs when is_git mode && String.is_prefix ~prefix:"rename from " x && String.is_prefix ~prefix:"rename to " y ->
       let git_action = Some (Rename_only (String.slice ~start:12 x, String.slice ~start:10 y)) in
@@ -367,20 +389,21 @@ let parse_one ~p data =
         in
         find_start ~mode ~git_action xs
     | x::y::xs when String.is_prefix ~prefix:"--- " x && String.is_prefix ~prefix:"+++ " y ->
-      Some (operation_of_strings ~p x y), xs
-    | x::y::_xs when String.is_prefix ~prefix:"*** " x && String.is_prefix ~prefix:"--- " y ->
-      failwith "Context diffs are not supported"
+      Some (operation_of_strings ~p x y), Unified_diff, xs
+    | x::y::"********"::xs when String.is_prefix ~prefix:"*** " x && String.is_prefix ~prefix:"--- " y ->
+      Some (operation_of_strings ~p x y), Context_diff, xs
     | _::xs -> find_start ~mode ~git_action xs
   in
   match find_start ~mode:None ~git_action:None data with
-  | Some (Rename_only _ as operation), rest ->
+  | Some (Rename_only _ as operation), _, rest ->
+      (* assert diff_kind = Unified_diff *)
     let hunks = [] and mine_no_nl = false and their_no_nl = false in
     Some ({ operation ; hunks ; mine_no_nl ; their_no_nl }, rest)
-  | Some operation, rest ->
-    let hunks, mine_no_nl, their_no_nl, rest = to_hunks (false, false, []) rest in
+  | Some operation, diff_kind, rest ->
+    let hunks, mine_no_nl, their_no_nl, rest = to_hunks diff_kind (false, false, []) rest in
     Some ({ operation ; hunks ; mine_no_nl ; their_no_nl }, rest)
-  | None, [] -> None
-  | None, _ -> assert false
+  | None, _, [] -> None
+  | None, _, _ -> assert false
 
 let to_lines = String.cuts '\n'